The Daleks ( ) are a fictional extraterrestrial race of mutant from the British science fiction television series Doctor Who. Within the series, Daleks are cyborgs from the planet Skaro, created by the scientist Davros as the last and greatest weapon in the war against the Thals. They are mutated Kaleds integrated within a tank-like or robot-like mechanical casing. The resulting creatures are a powerful race bent on universal conquest and domination, utterly without pity, compassion or remorse. Various storylines portray them as having had every emotion removed except hate, leaving them with a desire to purge the Universe of all non-Dalek life. Occasionally they are shown as experiencing other emotions, primarily fear, although such occurrences are rare. Collectively they are the greatest enemies of the series' protagonist, the Time Lord known as the Doctor. Their famous catchphrase is "Exterminate!", with each syllable individually synthesised in a frantic electronic voice.

The Daleks were created by writer Terry Nation and designed by BBC designer Raymond Cusick. They were introduced in December 1963 in the second Doctor Who serial, colloquially known as The Daleks. They became an immediate and huge hit with viewers, featuring in many subsequent serials and two 1960s motion pictures. They have become as synonymous with Doctor Who as the title character, and their behaviour and catchphrases are now part of British popular culture. "Hiding behind the sofa whenever the Daleks appear" has been cited as an element of British cultural identity; and a 2008 survey indicated that 9 out of 10 British children were able to identify a Dalek correctly. In 1999 a Dalek appeared on a postage stamp celebrating British popular culture, photographed by Lord Snowdon. In 2010, readers of science fiction magazine SFX voted the Dalek as the all-time greatest monster, beating out competition including Japanese movie monsterGodzilla and J. R. R. Tolkien's Gollum, of The Lord of the Rings.

The word "Dalek" has entered major dictionaries, including the Oxford English Dictionary, which defines it somewhat imprecisely as "a type of robot appearing in ‘Dr. Who‘, a B.B.C. Television science-fiction programme; hence used allusively." The term is sometimes used metaphor to describe people, usually figures of authority, who act like robots unable to break from their programming; for example, John Birt, the Director-General of the BBC from 1992 to 2000, was publicly called a "croak-voiced Dalek" by playwright Dennis Potter in the MacTaggart Lecture at the 1993 Edinburgh Television Festival A small wheeled stool used in libraries and offices to reach higher shelves is also colloquially known as a dalek.